In computer networks, it is often desirable for one node to transmit data over a network so the data can be received by all other nodes connected to the network. To accomplish the transmitting, a pool of multicast (group) addresses may be allocated to each network by a network standards body, such as the Institute of Electrical and Electronic Engineers (IEEE) or the American National Standards Institute (ANSI). Any node on the network can read data being transmitted on a multicast address. The standards body guarantees that allocated multicast addresses do not overlap between networks.
Traditionally, multicast addresses were assigned from the pool one at a time, each multicast address serving a specific purpose or function. For example, there are specific multicast addresses assigned for Ethernet end-station “hello” messages, LAT service announcements, and Fiber Distributed Data Interface (FDDI) status reporting frames. Each assigned multicast address serves one explicit function. To prevent a node that is receiving one data stream from being inundated by other data streams, a unique multicast address is required for each unique data stream.
A problem with the traditional assignment method is that each multicast address on a network is assigned for a single specific purpose or function. As the number of specific functions on the network increases, more multicast addresses from the network's allocated pool are assigned to meet the need. Once the network's pool of allocated multicast addresses is depleted, the network must be allocated an additional pool of multicast addresses. This in turn depletes more addresses from the finite set of addresses that are available to be allocated to the various networks.
While many multicast addresses may be allocated to a network and assigned by the network for specific functions, only a relatively few multicast addresses may be in use on the network at any one time. Indeed, many multicast addresses may be used infrequently because the associated functions are in low demand. Networks are thus expanding their pool of multicast addresses while not using all multicast addresses already allocated to the networks.